INDUCTIVE EPOCH OF NEWTON. 175 



after the publication of the Principia, and, with 

 Newton's methods, no one up to the present day, 

 had added anything of any value to his deductions. 

 We know that he calculated all the principal lunar 

 inequalities ; in many of the cases, he has given us 

 his processes ; in others, only his results. But who 

 has presented, in his beautiful geometry, or deduced 

 from his simple principles, any of the inequalities 

 which he left untouched? The ponderous instru- 

 ment of synthesis, so effective in his hands, has 

 never since been grasped by one who could use it 

 for such purposes ; and we gaze at it with admiring 

 curiosity, as on some gigantic implement of war, 

 which stands idle among the memorials of ancient 

 days, and makes us wonder what manner of man he 

 was who could wield as a weapon what we can 

 hardly lift as a burden. 



It is not necessary to point out in detail the 

 sagacity and skill which mark this part of the 

 Principia. The mode in which the author obtains 

 the effect of a disturbing force in producing a 

 motion of the apse of an elliptical orbit (the ninth 

 Section of the first Book), has always been admired 

 for its ingenuity and elegance. The general state- 

 ment of the nature of the principal inequalities pro- 

 duced by the sun in the motion of a satellite, given 

 in the sixty-sixth Proposition, is, even yet, one of 

 the best explanations of such action ; and the calcu- 

 lations of the quantity of the effects in the third 

 Book, for instance, the variation of the moon, the 



